A timepiece for indicating digital display of time information such as hour, minute, and second, and calendar information such as date, days of the week, month, and year, by use of a liquid crystal display panel (device), has been in widespread use for watches and clocks, provided with a crystal oscillation circuit.
There has also been in use a combination watch wherein analog display indicating time information by the hands of the watch is used in combination with digital display indicating time information and calendar information in numbers and letters.
Further, there has been proposed an analog watch for selectively displaying scales in various patterns, or for displaying simulated hands for an hour hand, a minute hand, and a second hand, by making up the dial thereof based on a liquid crystal display panel (refer to, for example, Japanese Patent Laid-open S54-153066).
A liquid crystal display panel, small in size and consuming very little electric power, has been in widespread use as a display panel for displaying necessary information (character information and graphic information) in various electronic equipment other than timepieces, such as cellular phones, desktop electronic computers, portable game players, and so forth.
In such a liquid crystal display panel, a liquid crystal cell filled with liquid crystals is sandwiched between two transparent substrates having an electrode on respective inner surfaces thereof, facing each other, and an upper polarizing film and a lower polarizing film are disposed, respectively, on the external surface of the transparent substrates, on the opposite sides. If an electric field is applied to the liquid crystals by applying a voltage to a pair of electrodes on the transparent substrates which hold the liquid crystal cell therebetween, the optical property of the liquid crystals is changed, thereby locally controlling transmission and absorption of light falling on the liquid crystal display panel such that a predetermined display is effected.
Either of the upper polarizing film and the lower polarizing film in the conventional liquid crystal display panel is a polarizing film absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof. Accordingly, light falling on the liquid crystal display panel is controlled to transmit though the two polarizing films or to be absorbed by either of the polarizing films, and there seen is a portion that appears light owing to direct light from a light source or a reflected light when the incident light is reflected on a reflection film, or a portion that appears black because of the interception of the incident light.
In the case of a watch using the conventional liquid crystal display panel described above, time information and calendar information are displayed in white against the black background in normally-black mode when displaying using a back-light illuminated by a light source incorporated therein.
However, in the case of displaying digital information of time and so forth in the liquid crystal display panel, the area of a region (background part) other than the area of the information display part is very large. Accordingly, when indicating digital display of time information and calendar information in white against the black background, light absorbed by the polarizing film is predominant compared with light that is actually used in display. Accordingly, most of the light emitted by the light source is wasted.
Accordingly, it is necessary to increase the amount of luminescence to display with high visual recognition, leading to an increase of the power consumption, causing a problem of shortening the life span of a battery, in the case of portable electronic equipment.
Further, in the panel merely indicating digital display of time information and calendar information in white against the black background, variation in design cannot be offered, with a tendency to quickly lose popularity among consumers. Probably as a result, consumption of digital watches has recently been on the decline. Neither combination watches nor analog watches with a liquid crystal display panel has since received market acceptance.
Similarly, in the case of transmission display by the light source incorporated therein with the conventional liquid crystal display panel used in other electronic equipment, various information expressed in letters and graphics is generally displayed in white against the black background, and although there are some wherein information can be displayed in black against the white background in an inverse mode, the liquid crystal display panel has been found still lacking in design variation and sense of amusement.
In light of the present situation as described, the present invention has been developed, and an object of the invention is to provide a liquid crystal display panel capable of indicating sufficiently visible display even at dark locations where no or little external light is available, and offering novelty and variation in design while ensuring a long service life of a battery used therein.